The subject disclosure relates to printing systems, their architecture and processing steps and, more particularly, to producing electronic images in a manner to drive digital printers more efficiently and faster.
Generating print-ready documents to be printed by a printing system involves acquiring the information (content, graphics, production specs, etc.) required to image, process and output the desired document in an electronic form understandable by a print engine. Such systems can range from those that are simple and modestly expensive such as are well known to consumer users of personal computer systems, up to commercial printing systems that are capable of generating in the range of one hundred pages per minute in full color. All systems though have a high level objective of printing faster. There are three general approaches which have been applied in the past for accomplishing this objective. First, faster serial processing methods suggest optimizing the software and using faster and more expensive processors. Second, job parallel processing sends separate jobs to separate systems and then prints them on a common printer. Third, Portable Document Format (“PDF”) based page parallel systems convert the job to PDF, and then split the PDF file into pages which are converted to print ready form on multiple independent processors, with the job being printed on a common printer. Software optimization has its limits and faster processors are also limited by currently available technology. Job parallel processing results in poor single job performance, unpredictable job time and reduced throughput when there is only one long job in the queue. The existing PDF-based solutions are slow due to their need to often convert from a different input language into PDF and then write the PDF file into an input spool disk. Page parallel processing has suffered from the inefficiencies of a throughput disadvantage because per job overhead occurs on a per page or per chunk basis. In addition, some print jobs are not splittable or cannot be split into pages printed in a page independent sequence.
A more detailed description of a job parallel system is in U.S. Pat. No. 5,819,014 which describes a printer architecture using network resources to create a “distributed” printer controller or translator. By distributing the translators across the network, print jobs may be processed in parallel. Each job is formatted in the system in a particular data type comprising a Page Description Language (“PDL”) such as a PostScript file, ASCII, PCL, etc. A distributed set of the translators is used for each data type, the translators each comprising a plurality of CPUs to simultaneously rasterize each data type. In real time operation, each translator on the network can formulate the rasterized image which is then fed over the network to the print engine. Job parallelism increases the flexibility of the printing system by allowing slow jobs to be processed while quicker jobs are completed and printing. However, it can be easily appreciated that where the jobs require substantially different processing times, waits will necessarily occur and overall system efficiency will suffer.
A well known commercially available system exploiting page parallelism is Adobe™ Extreme. In this system the data input for a print job is normalized into a PDF format and stored on disk. The PDF format is essentially page independent guaranteed and thus facilitates segregating the job into page units for page parallel processing. A “sequencer” processing node takes the PDF jobs off the disk and writes them back onto a disk again a page at a time as individual files, one file per page. Rasterizing image processing nodes (RIPs) then convert the files into a print-ready form acceptable by a print engine. It is important to note that in terms of processing efficiency, Adobe Extreme must access the disk twice, thus slowing the system down, and that the RIP nodes can only process a file consisting of a single page. Of course, an entire job may be limited to one page, but for purposes of setting the stage for the subject disclosure, when a job is comprised of several pages, Adobe Extreme must sequence it to individual pages only.
There are certain PDL files that are considered “non-splittable” by virtue of their language (e.g. PCL) or construction (e.g. non-DSC compliant PostScript). It is difficult to RIP such jobs at ever increasing rates by relying on improvements in processor speed, as computational vendors have focused their efforts on providing multiple-core CPUs rather than single CPUs with higher clock frequencies. “Non-splittable” PDLs cannot easily be processed by multiple RIPs running in parallel on these multiple core CPUs. The problem is presently addressed by 1) preprocessing the PDL file to convert it into a splittable PDL (e.g. PDF), or 2) preprocessing the PDL so as to create a series of instructions to direct the operation of RIPs operating in parallel on the PDL file or segments of the PDL file, or 3) by RIP coding improvements.
Accordingly, in the continuing need for improving efficiency and speed in printing systems, there is a need for a system which is not limited to mere job or page parallelism and that can facilitate control and data flow of a print job to the printing system that will obviate multiple accesses to a storage disk for any single job. The subject disclosure satisfies these needs and thus overcomes the problems specified above, as well as others.